Most trailers used in combination with large trucks utilize some variation of support legs or “landing gear” to keep the trailer level when not engaged with a truck and so as to allow the trailer to be easily attached and detached from a truck. These legs come in a variety of styles, but most have the overall basic form as shown in FIG. 1, where a conventional landing gear 10 for a semi-trailer is shown. The landing gear 10 is used to support a semi-trailer when the semi-trailer is disconnected from a tractor. The landing gear 10 is designed to expand and contract vertically. In expansion, the landing gear 10 lifts the front of a semi-trailer so that it can be disconnected from the tractor, and thereafter supports the front of the semi-trailer when the tractor departs. In contraction, the landing gear 10 lowers the front of the semi-trailer to enable connection to a tractor, and, once connected, to further gain ground clearance so the semi-trailer can be pulled by the tractor without the supports striking the ground.
The landing gear 10 typically comprises a pair of spaced arms 12, each having a mounting bracket 26 for securing the landing gear to a frame of a semi-trailer (not shown). Each arm 12 comprises a hollow tube 16 within which is a leg 14 that is geared to extend from and retract into the hollow tube 16. Each leg has a foot pad 18 that supports the landing gear 10 on the ground. A gearbox 20 may be mounted to one of the arms to control the extension and retraction of both legs by way of a cross drive shaft 22 extending between the arms 12. The gearbox 20 is manually driven by a crank handle 24. In other examples, the legs may be raised and lowered using pneumatic, hydraulic, or electrical power rather than with a hand crank.
When a trailer is parked without an attached truck it is vulnerably to theft by simply attaching another truck to the unattended trailer and driving away. Several different methods have been used to help secure unattached trailers, most of which involve securing or otherwise disabling the attachment point of the trailer (i.e., the kingpin) or removing or disabling the raising and lowering mechanism of the legs. Such methods are generally easy to defeat for a thief who comes prepared with cutting tools and/or replacement hardware to remove any securing devices and/or enable the trailer legs.